ucx: src/hash_map.c@d7f0b5a9a985

     1 /*

     2  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.

     3  *

     4  * Copyright 2021 Mike Becker, Olaf Wintermann All rights reserved.

     5  *

     6  * Redistribution and use in source and binary forms, with or without

     7  * modification, are permitted provided that the following conditions are met:

     8  *

     9  *   1. Redistributions of source code must retain the above copyright

    10  *      notice, this list of conditions and the following disclaimer.

    11  *

    12  *   2. Redistributions in binary form must reproduce the above copyright

    13  *      notice, this list of conditions and the following disclaimer in the

    14  *      documentation and/or other materials provided with the distribution.

    15  *

    16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"

    17  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

    18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

    19  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE

    20  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR

    21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF

    22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

    23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

    24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)

    25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE

    26  * POSSIBILITY OF SUCH DAMAGE.

    27  */

    29 #include <string.h>

    30 #include "cx/hash_map.h"

    32 /**

    33  * Computes a murmur hash-2.

    34  *

    35  * @param data the data to hash

    36  * @param len the length of the data

    37  * @return the murmur hash-2 of the data

    38  */

    39 static unsigned cx_hash_map_murmur(

    40         unsigned char const *data,

    41         size_t len

    42 ) {

    43     unsigned m = 0x5bd1e995;

    44     unsigned r = 24;

    45     unsigned h = 25 ^ len;

    46     unsigned i = 0;

    47     while (len >= 4) {

    48         unsigned k = data[i + 0] & 0xFF;

    49         k |= (data[i + 1] & 0xFF) << 8;

    50         k |= (data[i + 2] & 0xFF) << 16;

    51         k |= (data[i + 3] & 0xFF) << 24;

    53         k *= m;

    54         k ^= k >> r;

    55         k *= m;

    57         h *= m;

    58         h ^= k;

    60         i += 4;

    61         len -= 4;

    62     }

    64     switch (len) {

    65         case 3:

    66             h ^= (data[i + 2] & 0xFF) << 16;

    67                     __attribute__((__fallthrough__));

    68         case 2:

    69             h ^= (data[i + 1] & 0xFF) << 8;

    70                     __attribute__((__fallthrough__));

    71         case 1:

    72             h ^= (data[i + 0] & 0xFF);

    73             h *= m;

    74                     __attribute__((__fallthrough__));

    75         default:

    76             /* do nothing */;

    77     }

    79     h ^= h >> 13;

    80     h *= m;

    81     h ^= h >> 15;

    83     return h;

    84 }

    87 /**

    88  * Creates a hash map key based on the given data.

    89  *

    90  * This function implicitly computes the hash.

    91  *

    92  * @attention The data will be copied to the key structure.

    93  *

    94  * @param data the data for the key

    95  * @return the computed key

    96  */

    97 static struct cx_hash_map_key_s cx_hash_map_key(CxDataPtr data) {

    98     unsigned char *target = malloc(data.len);

    99     memcpy(target, data.data, data.len);

   100     struct cx_hash_map_key_s key;

   101     key.data.data = target;

   102     key.data.len = data.len;

   103     key.hash = cx_hash_map_murmur(target, data.len);

   104     return key;

   105 }

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